const GITHUB_PATH_SEGMENT = /^[A-Za-z0-9_.-]+$/u;

type ParsedProjectGitUrl = {
  url: string;
  name: string;
};

function githubPathParts(pathname: string): { owner: string; repo: string } | null {
  const segments = pathname.split("/").filter(Boolean);
  const owner = segments[0];
  const repo = segments[1]?.replace(/\.git$/iu, "");
  if (
    segments.length !== 2 ||
    !owner ||
    !repo ||
    !GITHUB_PATH_SEGMENT.test(owner) ||
    !GITHUB_PATH_SEGMENT.test(repo) ||
    owner === "." ||
    owner === ".." ||
    repo === "." ||
    repo === ".."
  ) {
    return null;
  }
  return { owner, repo };
}

/** Canonicalizes the GitHub clone forms accepted by projects.add. */
export function parseProjectGitUrl(raw: string): ParsedProjectGitUrl | null {
  const trimmed = raw.trim();
  if (!trimmed || trimmed.startsWith("-") || trimmed.includes("\0") || /[\r\n\t ]/u.test(trimmed)) {
    return null;
  }

  const scp = /^git@github\.com:(.+)$/iu.exec(trimmed);
  let parts: { owner: string; repo: string } | null;
  if (scp) {
    parts = githubPathParts(scp[1] ?? "");
  } else {
    try {
      const url = new URL(trimmed);
      const isHttps = url.protocol === "https:";
      const isDefaultSsh =
        url.protocol === "ssh:" && url.username === "git" && (!url.port || url.port === "22");
      if (
        (!isHttps && !isDefaultSsh) ||
        url.hostname.toLowerCase() !== "github.com" ||
        url.password ||
        (isHttps && url.username) ||
        url.search ||
        url.hash
      ) {
        return null;
      }
      parts = githubPathParts(url.pathname);
    } catch {
      return null;
    }
  }
  if (!parts) {
    return null;
  }
  return {
    url: `https://github.com/${parts.owner.toLowerCase()}/${parts.repo.toLowerCase()}.git`,
    name: parts.repo,
  };
}